Patent Application
20100000935
The invention relates to a membrane unit and a membrane element suitable to be used as a membrane filtration apparatus particularly for wastewater treatment and water purification treatment.
As a membrane separation technique to be applied for wastewater treatment has been known a technique of obtaining membrane-filtered water by immersing a membrane unit in which a plurality of membrane elements are arranged and inserted in a treatment tank filled with wastewater such as activated sludge and by suctioning the filtered water side of the membrane unit by a pump, or discharging water based on the water level difference just like a siphon.
In the case of activated sludge process, to propagate aerobic microorganism in the treatment tank, air diffusion to the tank is required. If an apparatus for air diffusion is installed down below a membrane unit, the gas-liquid mixing flow by the air diffusion can ascend in the membrane unit and scrape contamination of the membrane surfaces (membrane faces). As a result, solid-liquid separation can be carried out while the cleaning of the membrane surface is carried out, and thus the membrane filtration operation can be carried out at a low cost.
At that time, if the velocity of the gas-liquid mixing flow for scraping the membrane surfaces is high, stable operation can be continued. As means for increasing the velocity of the gas-liquid mixing flow, as shown in
Further, in order to carry out membrane filtration operation stable, it is also important to keep the intervals of raw water channels formed between respective membrane elements constant, and for example, a membrane unit obtained by setting a plurality of membrane elements having projected parts (spacer parts) in the circumferential rim parts in a casing while bringing the spacer parts of adjacent membrane elements into contact with each other has been also disclosed (see Patent Document 3). Accordingly, a gas-liquid mixing flow can be evenly sent close to the membrane surface of each membrane element, and the membrane surface of each membrane element can be washed evenly.
However, in the above-mentioned techniques described in Patent Documents 1 and 2, in order to increase the velocity of the gas-liquid mixing flow, it is required to install the housing, being an additional member, on the upper parts of membrane element. As the membrane unit, since the membrane elements are contained in a housing 83 with a size corresponding to a desired number of membrane elements, it is also required to adjust the size of the housing 84 depending on the size of the housing 83. That is, it is required to produce upper housings 84 with various sizes depending on the number of membrane elements, and thus there is a problem regarding the efficiency in terms of the apparatus production. Further, if the velocity of the gas-liquid mixing flow is further increased, the pulsation becomes intense and therefore a preferable state for removing contaminations from the filtering membrane surfaces 71 is produced. On the other hand, an excess load is applied to the membrane elements 71, and therefore, the displacement of membrane elements tends to occur. Furthermore, a supporting plate bends considerably and tends to deform, the spacer parts move slightly, and thus a problem of causing wear tends to occur.
The method of increasing an air amount is a preferable for removing contaminations of the filtering membrane surface because of a strenuous pulsation. On the other hand, since an excess load is applied to the supporting plate of the membrane element, the displacement of the membrane elements tends to occur. Furthermore, the supporting plate bends considerably and tends to deform, the spacer parts move slightly, and thus a problem of causing wear tends to occur. Furthermore, in a case where the membrane unit apparatus in which intervals of the raw water channels are kept constant by bringing the above-mentioned spacer parts into contact with each other, there is a problem that the intervals of the raw water channels of membrane faces are easily fluctuated due to vibration of the membrane elements generated during the operation.
In order to prevent the displacement of the membrane elements even if a load is applied due to the high velocity gas-liquid mixing flow in an immersion tank and keep the intervals of the membrane surfaces constant, it has been also proposed that a membrane unit is assembled by arranging a plurality of membrane elements having spacer parts in both right and left sides of supporting plates in such a manner that the spacer parts are brought into contact with each other and uniting the membrane elements by inserting through bolts into holes formed in the supporting plates (see Patent Document 4). In the case of this membrane unit, in order to prevent slight movement wear in the contacting spacer parts, the through bolts 45 have to be fastened to make the fastening force of the contacting spacer parts higher than the force applied to the supporting plates, and then the slight movement of the spacer parts can be prevented.
However, with the membrane unit structure described in that document, if the through bolts are fastened firmly, particularly the supporting plates themselves of membrane elements at the outside positions bends considerably to result in a problem that the supporting plates are broken or the spacer parts cannot be brought into contact since the fastening positions of the spacer parts and the through bolts are apart, and the slight movement wear is further promoted.
An object of the invention is to solve the above-mentioned problems and provide a membrane element, a membrane unit, and a multi-deck membrane unit with which a space part surrounded with a frame body can easily be installed above the membrane element regardless of a number of the membrane element and wear of spacer parts can be suppressed. Another object of the invention is to provide a membrane element, a membrane unit, and a multi-deck membrane unit with which air supplied from the lower part of the membrane element can efficiently be utilized and the efficiency in terms of an apparatus production can be improved.
In order to accomplish the objects, the invention includes the following configuration. That is:
(1) a membrane element comprising filtering membranes on both surfaces of a plate-like supporting plate, wherein spacer parts are formed at both side parts of the membrane element for keeping prescribed distance to the surface of an adjacent membrane element, and the spacer parts have through bolt insertion holes and are extended upward from the upper end part of the supporting plate;
(2) The membrane element according to (1), wherein the through bolt insertion holes are U-shape holes opened to the side face of the membrane element and penetrating form the front surface to the rear surface of the membrane element;
(3) The membrane element according to (1) or (2), wherein projection part for fitting and reception part for fitting are formed in the spacer part for positioning with an adjacent membrane element;
(4) The membrane element according to any one of (1) to (3), wherein a channel part having a through hole for forming a water collecting pipe is formed in the upper part of the spacer part and the through hole in the channel part and the inside of a filtered water chamber formed by the filtering membranes disposed on both surfaces of the supporting plate are communicated;
(5) A membrane unit having a plurality of membrane elements according to any one of (1) to (4) arranged in such a manner that the spacer parts are brought into contact with each other, seal panels are installed to outermost parts of the arranged membrane elements, and a frame body surrounding the space above the filtering membranes is formed by the spacer parts and the seal panels;
(6) A membrane unit comprising a plurality of membrane elements according to (2) arranged in such a manner that the spacer parts are brought into contact with each other, and seal panels having through bolt insertion holes are installed to the outermost parts of the arranged membrane elements, wherein the membrane elements and the seal panels are united by inserting through bolts into the U-shape holes of the membrane elements and the through bolt insertion holes of the seal panels;
(7) A membrane unit comprising a plurality of membrane elements according to (4) arranged in such a manner that the channel parts formed in the spacer parts are brought into contact with each other, seal panels are installed to the outermost parts of the arranged membrane elements, a frame body surrounding the space above the filtering membranes is formed by the spacer parts and the seal panels, and a water collecting pipe is formed by bringing a plurality of the channel parts into contact with one another;
(8) A multi-deck membrane unit comprising the membrane unit apparatus according to any one of (5) to (7) layered vertically in multi-decks.
In this invention, phrases such as “both side parts”, “upper end part”, “above”, “side face”, “outermost part” and the like are determined on the basis of the state at the time of use.
Since the spacer parts in both right and left sides are extended above the upper end part of the supporting plate, a plurality of the membrane elements of the invention can be arranged in such a manner that the distances of raw water channels to be formed between the respective membrane elements are kept constant by bringing the spacer parts into contact with one another; and further, a membrane unit without requiring an additional housing and a frame body surrounding the space above the filtering membranes can be formed by bringing the seal panels into contact with one another. According to the invention, regardless of the number of the membrane elements and the size of the membrane units, a space can reliably be kept above the membrane elements. Accordingly, air supplied from the lower part of the membrane units can be efficiently utilized for scraping the contaminations on the membrane surfaces (membrane faces) and stable membrane filtration operation is made possible. Further, without installing an upper housing according to prior arts, the membrane unit can be easily layered in multi-decks and it is advantageous in terms of the cost, and the space shape between upper and lower decks is always kept constant and controlled gas-liquid mixing flow can be efficiently utilized. In addition, the vibration of spacer parts due to pulsation is suppressed and wear is decreased by inserting through bolts into the through bolt insertion holes of the spacer parts and fastening a plurality of the membrane elements. In this case, the through bolts do not interrupt the gas-liquid mixing flow.
In the case where holes for through bolt insertion penetrate from the front surface to the rear surfaces of membrane elements and are U-shape holes opened to the side face of the membrane elements, through bolts can be easily inserted even in that state that several tens to a hundred and several tens of the membrane elements are layered. In the case where the projection part for fitting and reception part for fitting for positioning with an adjacent membrane element are formed in the spacer parts, the membrane elements can be easily and evenly layered. Further, in the case of membrane elements having channel parts in the upper parts of the spacer parts, the membrane unit is configured by arranging a plurality of the membrane elements while bringing the channel parts into contact with one another and also bringing the seal panels into contact with one another, so that the water collecting pipe for taking filtered water out can be formed in the upper part of the membrane unit. As a result, a tube for taking out filtered water is not necessary and thus the membrane unit can be easily multi-layered without particular work (e.g. formation of through holes for leading a tube to the outside of a module) of the wall parts forming the space parts above the membrane elements.
Hereinafter, the invention will be described in detail with reference to drawings of embodiments of the invention.
The membrane element 1 shown in
A nozzle-like filtered water outlet 17 is at the upper end part of the supporting plate 12. On the other hand, sheet-like filtering membranes 11 are installed on both front and rear surfaces of the supporting plate 12, and a filtered water flowing space (filtered water chamber) is formed in the inside of the filtering membranes. The filtered water outlet 17 is connected to the filtered water chamber between the filtering membranes 11 and the supporting plate 12 via a channel 18. The filtered water flowing into the filtered water chamber after filtered from the outside of the filtering membranes 11 is discharged out of the filtered water outlet 17 via the channel 18.
The supporting plate 12 is not particularly limited as long as it is an approximately flat plate-like one. A material for that is not particularly limited as long as it is a material having toughness equivalent to a bending elastic modulus of about 300 MPa according to ASTM testing method D790 (2003); however, metals such as stainless steels, resins such as acrylonitrile-butadiene-styrene rubber (ABS resin) and vinyl chloride, composite materials such as fiber-reinforced resin (FRP), and other materials may be properly selected and used.
The spacer parts 13 are thick parts installed at both side parts of the supporting plate 12, and as shown in
In the spacer parts 13, through bolt insertion holes 14 are formed. As shown in
The shape of the through bolt insertion holes 14 being formed in the spacer parts 13 is not particularly limited and may be determined corresponding to the fastening force required for the spacer parts. However, as shown in
Further, the number and the size of the through bolt insertion holes 14 may be also determined depending on the fastening force required for the spacer parts. The fastening force required for the spacer parts is, for example, a stress of 1 kg/cm2 (9.807×104 Pa) or higher, and it is preferable to determine it together with the specification of the through bolts 46 so as to give the fastening stress. For example, in the case where through bolts 46 of M12 to M16 (made of SUS 304) are used, it is preferable to form through bolt insertion holes 14 with a diameter (circular) larger than that of bolts by 0.5 to 3 mm at 100 to 1000 mm pitches in both spacer parts.
In
Further, in the case where the load by the gas-liquid mixing flow is very high and the fastening force for the spacer parts has to be increased more, it is supposed to employ methods of increasing the number of the through bolts or widening the diameter of the through bolts; however in both cases, disadvantageous phenomena would be caused. In the case of increasing the number of the through bolts, there occur a problem of cost increase for the through bolts and a problem of complication in the assembling a membrane unit 42. In the case of widening the diameter of the through bolts to increase the fastening force, there also occur a problem that the cost is increased for the supporting plate since the width of the spacer parts has to be wide depending on the diameter of the bolts and a problem that it becomes difficult to evenly fasten the respective parts of the spacer parts since the area of the parts to be brought into contact with the adjacent membrane elements is widened.
Therefore, in order to solve these problems, it is also preferable to form ribs 23 intermittently at the outside parts of the spacer parts 13 as shown in the membrane element 1 shown in
Further, it is also preferable to form projection parts 21 for fitting and reception parts 22 for fitting it in the spacer parts 13 as shown in the cross-sectional view of
The extended parts 15 may have a structure formed simply by extending the spacer parts 13 upward higher than the upper end parts of the membrane elements 1 as shown in
The entire circumferential rim parts of the filtering membrane 11 are liquid-tightly fixed to the supporting plates 12 by means such as melt deposition, fusion, adhesion, or the like to partition the filtering membranes 11 in which the outer face is raw water side and the inner face is filtered water side. The filtering membranes 11 are not particularly limited, in the case of solid-liquid separation of activated-sludge water, a flat membrane type filtering membrane with a pore diameter determining the filtration capability of the filtering membranes 11 in a range of 0.01 to 20 μm is preferable.
The membrane elements 1 composed of the above-mentioned parts are assembled to form membrane units shown in, for example,
The membrane units 42 of the invention shown
The seal panels 45 are plate-like ones for covering the outermost parts of the arranged membrane elements 1, and in the case of integration by through bolts, through bolt insertion holes 52 are formed. Since the respective raw water channels 51 between membrane elements 1 are preferable to have approximately uniform width, it is preferable to install spacer parts to the both right and left side parts (the side brought into contact with the spacer parts 13 of the membrane elements) of the inner side faces of the seal panels 45 so as to form the raw water channels 51 with approximately same width between the membrane elements as shown in
The through bolts 46 are not particularly limited as long as they can integrate and fix the seal panels 45 and a plurality of membrane elements 1 by penetration. The number of the through bolts and the bolt diameter may be properly set depending on the fastening force and weight of the membrane unit 42. At the time of fixation of the through bolts 46, it is preferable to fix them by setting nuts 50 at both ends. In the case of layering a plurality of membrane elements 1, while the spacer parts 13 of adjacent membrane elements are brought into contact with one another, the membrane elements are arranged, and in this case, the extended parts 15 are brought into contact with one another. Accordingly, the extended parts 15 of the spacer parts 13 form walls at the upper and two opposed side faces of the membrane unit. Further, the seal panels 45 are layered at the outermost parts of the membrane elements 1, and walls are formed at remaining two opposed side faces of the membrane unit by the upper parts of the seal panels 45 by using those having a shape covering the extended parts 15 for the seal panels 45. That is, a frame body 48 surrounding the space above the filtering membranes is formed by the extended parts 15 and the seal panels 45, and by the frame body 48, a space part 49 above the membrane elements 1 can be reliably retained. Accordingly, the speed of the gas-liquid mixing flow can be increased without installing upper housing, being an additional part, above the membrane elements.
In the case of using membrane elements having spacer parts 13 having the projection parts 21 for fitting and reception parts 22 for fitting it as shown in
The membrane elements 1 and the seal panels 45 are united by the through bolts 46. At the time of uniting them, through bolts 46 are fitted into the through bolt insertion holes 14 of a plurality of the arranged membrane elements 1 from the side and then inserted into hole parts 52 of one seal panel 45. Thereafter, the membrane elements are moved to bring the spacer parts into contact with one another. After a prescribed number of membrane elements are arranged, the through bolts 46 are inserted into hole parts 52 of the other seal panel 45 and fixed by nuts 50. In such a manner, the membrane unit 42 can be assembled.
In the case where the through bolt insertion holes 14 are opened to the side face, the assembly space necessary for inserting the through bolts 46 into a plurality of the membrane elements 1 can be narrowed as compared with that in the case where the holes have a simple hole shape not opened to the side face, and further the through bolts 46 can be easily inserted. The more the number of the membrane elements 1 is increased, the more effect of saving the space is significant. In addition, the holes to be formed in the seal panels 45 are made simple circular holes not opened to the side, so that the through bolts 46 can be prevented from dropping by tremors during the operation.
At the time of uniting the membrane elements 1 and the seal panels 45, as shown in
Further, in the case of the membrane unit as shown in
The membrane unit 42 assembled in such a manner is used as a membrane module 41 by installing the air diffuser 44 for jetting air under the unit. The air diffuser 44 may be fixed in a stand 43 mounting the membrane unit 42 thereon as shown in
As shown in
As shown in
As shown in
In the water treatment apparatus configured in such a manner, the water 61 to be treated such as wastewater is passed through the filtering membranes installed in the membrane elements 1 by suctioning force of the pump. In this time, microorganism particles and suspended solid such as inorganic particles or the like contained in the water 61 to be treated can be filtered and remain in the water 61 side. The water passing through the filtering membranes (filtered water) is taken outside of the treatment tank 63 from the spaces (filtered water chambers) between the supporting plates and filtering membranes via the water collecting pipes and the like. On the other hand, simultaneously with the membrane filtration, air is jetting from the air diffuser 44 and enters to the raw water channels of the membrane units. The ascending gas-liquid mixing flow parallel to the membrane faces of the membrane elements 1 generated by ascending air separates the filtered matter deposited on the membrane faces and washes the membrane faces.
The membrane elements and membrane units of the invention can be used in the case of water filtration treatment while being installed in a treatment tank and can be utilized for wastewater treatment and water purification treatment.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-085201 | Mar 2006 | JP | national |
| 2006-117580 | Apr 2006 | JP | national |
| 2006-117581 | Apr 2006 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/051957 | 2/6/2007 | WO | 00 | 3/16/2009 |
